1. Field of the Invention
This invention relates to a data recording device and a data reproducing device for recording data supplied from an information processing device, such as a personal computer or a work station.
2. Description of the Related Art
Up to now, a so-called data storage device has been known as a recording/reproducing apparatus capable of recording/reproducing digital data for a magnetic tape. Depending on the tape length of a tape cassette, as a media, such data storage device can have a voluminous recording capacity of the order of tens to hundreds of gigabytes. For this reason, such data storage device is widely used for backup of data recorded on a media, such as a hard disc of a main body member of a computer. The data storage device is also conveniently used for storage of picture data of a large data size.
As such data storage device, such a device is proposed in which data is recorded and/or reproduced in accordance with a helical scan system by a rotary head using, for example, a tape cassette of an 8 mm VTR.
In the above-described data storage device employing an 8-mm VTR tape cassette, a small computer system interface (SCSI), for example, is used as an input/output interface for recording/reproducing data.
During recording, data supplied from, for example, a host computer, is entered via SCSI. This input data is transmitted in terms of a pre-set fixed length data set as a unit. The input data is compressed in accordance with a pre-set system, if necessary, so as to be stored temporarily in a buffer memory. The data thus stored in the buffer memory is furnished to the recording/reproducing system in terms of a pre-set fixed length, termed a group, so as to be recorded by a rotary head on a magnetic tape of a tape cassette.
During reproduction, data of a magnetic tape is read out by the rotary head for storage transiently in a buffer memory. The data from the buffer memory, if previously compressed, is expanded so as to be sent via SCSI to the host computer.
Meanwhile, data on the magnetic tape forms a partition with which to enable data reproduction or data writing. The data recording unit in a given partition can be divided in terms of pre-set units termed groups, as described above, so that recording on the magnetic tape can be done based on this group unit. The end of the partition data area is clarified by an end-of-data (EOD) area in which only the information specifying the end of the data area is recorded.
If it is desired to append data in such data storage device, it is necessary to move to a directly previous group, that is the last group, after confirming the end of the data area by the EOD area, in order to acquire the count information recorded in this last group along with data, such as group count, file mark count, save set count or record count, as well as the data appending point information. That is, if data is to be appended in the conventional data storage device, the last group directly previous to EOD needs to be read, thus complicating the operation.
In addition, if dust and dirt, for example, is affixed to the rotary head to render it impossible to read the last group itself, the data appendage operation itself becomes impossible.